Investing is mostly skill based on knowledge--but you can't discount luck. When it comes to investing in the "right" company, sometimes even the savviest of investors get it wrong. Maybe they invested in a dud, which of course hurts. However, it's even worse when you pass up on a golden opportunity. Here are seven companies investors would give an arm or a leg to have bought into early (and why you should keep an eye on them still).

1. True Religion

The king of penny stocks, Tim Sykes, says that what happened with this Vancouver, Canada company is something nobody saw coming. It started as a penny stock company trading at $0.67 in 2004, and nine years later averaged $32 per share. That's a spike of 4,676 percent, thanks to the designer jeans with staying power.

2. BJ's Restaurants

Back in 1997, the small chain was trading at barely $1 per share--today it's at around $35, spiking in 2012 at $35. Early investors have enjoyed a 28,000 percent return thanks to perseverance and patience. Slow and steady really can win the (investment) race in some cases.

3. Monster Beverage

Did you know the company behind Monster, Hansen Natural, has been in business since 1935? Hansen Natural still doles out beverages, but in 1995 when Monster debuted it barely was worth $0.69 per share. It enjoyed 10,000 percent growth to achieve a high of $70 per hare thanks to getting named a "desirable takeover" option from Real M&A.

4. Pier 1 Imports

First Pier 1 was successful, then it almost went bankrupt during the recession--but the post-recession comeback is where many would-be investors missed their chance. After trading at $25 in 2003, stocks fell to $0.11 in 2009. Today, it's recovered at an 18,500 percent improvement to achieve pricing of over $20 per share.

5. Microsoft

True, many of today's investors weren't old enough (or even born yet) to be able to get in on Microsoft's IPO. However, if you'd been able to buy the $21 per stock IPO back in 1986 by picking up 100 shares, today you'd be basking in $750,000. Hindsight and all of that, but consider it a reminder that there's likely a Microsoft of today ripe for picking.

6. Twitter

With Twitter's IPO, 1,600 people legendarily became millionaires for the first time, although most of them were employees. The actual details of these newly minted millionaires are private, but it was calculated based on how many shares were held by investors on opening day, which closed at $40 per share.

7. Apple

In 1980, when Apple released its IPO at $22 per share, 4.6 million shares were sold to some very wise and lucky investors. The shares sold out in minutes, which beat Ford's previous record from 1956. Unsurprisingly, the investor who made out with the most was Steve Jobs himself, who earned $217 million on opening day.

Can you make millions by investing in the right company? Of course--but if it were easy, there would be a lot more millionaires. If you're a newbie, try to avoid playing around with stocks by yourself. Instead, start by working with a reputable broker and learn from someone with extensive experience.